FIG 4.

GDP analogues inhibit the GpppA formation catalyzed by the VSV L protein. The oligo-RNA capping assay was performed with 0.25 μM [α-³²P]GDP and 2.5 μM pppAACGA in the presence or absence of various concentrations of 2,6-diaminopurine-riboside 5′-diphosphate (DAPDP) (A), IDP (B), or ribavirin 5′-diphosphate (RDP) (C). The resulting GpppAACAG was analyzed as described for Fig. 1A. The results are expressed as percentages of the GpppA formation activity observed in the absence of the inhibitors (set to 100%) (D). Symbols and error bars represent the means and standard deviations, respectively, for three independent experiments.